The University of California, San Francisco (UCSF) is requesting funds for the purchase of a CyTOF C5 Mass Cytometer by DVS Sciences with Cytobank advanced data management and analytical software. Mass cytometry is a transformational new technology unavailable at UCSF that permits the identification and investigation of rare, diseased cells. The CyTOF mass cytometer marries the resolution, specificity, and sensitivity of atomic mass spectrometry to the high-throughput, single-cell analytical advantages currently provided by flow cytometry. Using stable isotopically pure (non-radioactive) metal tags, as many as forty parameters per single cell can be identified and quantified simultaneously, yielding unique biomarker signatures that distinguish a more refined analysis of cell populations. DVS Sciences is the only mass cytometer manufacturer. The impetus for this application is UCSF's missing mass cytometer capability. There are 43 scientific projects by 21 investigators from 12 different UCSF departments providing justification for funding. Acquisition of the CyTOF mass cytometer will create a shared resource with a projected usage over 2500 hours per year, demonstrating a real need for this technology. Four investigators are currently using the technology through inefficient long-distance collaborations. Clinical biopsies and human samples represent over 80% of the estimated usage of this system, potential biohazards not easily accommodated at other institutions. In response to this technology need, UCSF in a $2M renovation project is building a designated BSL2 (biosafety level) room for a mass cytometry resource. This resource will be part of an existing core facility and includes the ability to construct novel metal-tagged probes, manage CyTOF instrument operation, employ sophisticated software tools for managing and analyzing multi-parametric mass cytometer data, offer continued training and support to the user base, and educational courses to UCSF students. Institutional support will total 17% of the final cost for the CyTOF M5 Mass Cytometer.